Hamamelistes spinosus Shimer.

Host Hamamelis virginiana L.

The galls in this species are modified flower buds. These are some- what elliptical in outline with gradually tapering stalks. They are covered with spines, which are usually curved. The opening is situated at the union of the stalk and the gall proper. This opening is funnel- shaped and is surrounded by a circular ring of tissue as in the preceding species on the same host. The pubescence is absent in this case.

Dimensions: — Average length including stalk 21 mm.; average width 10 mm.

This gall is covered by an unusually small-celled epidermis. The spines that are so noticeable a feature are found to consist of projections of the epidermis, filled with cells in continuity with the mesophyll. The cells of the gall are almost perfectly circular in outline and packed together very closely. This tissue is very uniform except in the four or five layers adjoining the gall cavity. In that zone the cells are smaller and richer in protoplasmic contents, constituting a fairly well marked nutritive layer.

In cross section of the gall about thirty main fibro-vascular bundles are cut; these are comparatively large and situated near the larval cavity. Two of these have been cut in the section shown in Fig. 10. Other smaller strands are cut further out. The gall receives all the fibrovascular strands that, under normal conditions, would have passed up into the flower. The interior of both this and the preceding species is almost perfectly glabrous.

Hamamelistes spinosus

Records:
Hamamelis japonica, DC
Betula nigra, UT, WI

Hosts: Hamamelis virginiana; Betula alleghaniensis, lenta, nigra

Location: Flower bud

Range: Eastern North America